Method of briquetting coal



NOV. 12, 1935 R JJPlERSQL 202l,020

METHOD OF BRIQUETTING COAL Filed March 9, 1934 2 Sheets-Sheet 2 Patented Nov. 12, 1935 UNITED STATES 2,021,020 METHOD or BRIQUETTING' COAL Robert J. Piersol Champaign, n1.

Application March 9, 1934, Serial No. 714,760

8 Claims.

This invention relates to the formation of strong, stable briquettes from coal without the aid of added binders.

'More specifically, this invention relates to a process for impacting bituminous coal into strong briquettes which burn like lump bituminous coal or, if subjected to partial volatilization before briquetting, burn like lump anthracite coal. The invention also includes the briquettes formed by the process.

It is known that a, large proportion of the bituminous coal mined is produced in particles less than 2" in size, which are undesirable for commercial or domestic use. These small particles of less than 2" in size are known to the trade as fines or fine coal and constitute a drug on the market. Since they cannot be sold at a profit, the cost of mining lump size coal is considerably increased.

About one-half of the quantity of .fines produced occur in sizes of orless. These particles are of a size which is especially well adapted for the formation of briquettes. The other larger particles of the fines, i. e., from to 2",

maybe sold as screened finesor may be ground to sizes suitablc'for briquetting. If desired, the fines may be cleaned to lower their ash content before use. i i

It is therefore apparent that any cheap method of forming coal fines into lumps of usable size would be highly desirable. Many briquetting processes have been attempted. However, heretoiore, the only operative processes required the use of added binders which increase production costs so as to render these processes unsatisfactory from an economic, commercial standpoint.

Attempts to form briquettes from coal fines without added binders have never heretofore reached a. commercial scale since the lumps thus produced are, previous to carbonization, weak and deteriorate rapidly. In some instances, briquettes made from moist coal or moist coal and coke breeze compressed in a press were formed sufficiently to hold their shape in a subsequent carbonizatio-n process. The moisture, in these processes, acts as a temporary binder and carbonization of the moist briquette then removes the moisture and part of the volatile matter of the coal. The coal residue retains its lump shapes The formation of briquettes without binders under a pressure which is applied for any appreciable period of time has always produced briquettes which disintegrate and deteriorate rapidly. Furthermore, in many instances, the so formed briquettes explode or go to pieces burning.

Carbonization has heretofore been necessary to impart strength to briquettes formed without binders. I have now'found that bituminous coal fines may be impacted to produce raw fuel briquettes of high stability and permanent strength.

The briquettes of this invention are formed by impacting raw bituminous coal fines or partly volatilized fines to produce strong briquettes. Furthermore, if desired, the briquettes of this invention may be carbonized after formation.

According to my invention, any coal containing bituminous matter (the chief component of both vitrain and clarain) and fixed carbon (the major 15 component of fusain and a minor component of both vitrain and clarian) can be formed into stable and strong briquettes by being subjected, while heated to temperatures between 100 degrees and 400-degrees C., to an impact pressure such as is 20 obtained by the dropping of a weight onto a die containing the heated coal or the impact obtained by an impact ram acting against a die. Since the pressure is applied to the coal for only a small fraction of time, the resulting briquette is free 2 from internal stresses and will not disintegrate upon burning. The bituminous matter portion of the coal is, at the temperatures and impact pressures indicated, reduced to a somewhat plastic state and goes into the spaces between the fixed carbon particles to act as a binder for these particles.

vitrain,.itself, is exceedingly fragile and shatters along the lines of stress. It is shiny black in appearance and'resembles unannealed glass. vitrain, itself, cannot be formed into a stable briquette, and-I have likewise found that fusain cannot be formed into a stable briquette. However, a combination of both iusain and vitrain in a fuel can, according to my process, be formed 40 into a very stable briquette.

Clarain naturally occurs with the proper proportionr of bituminous and fixed carbon 00 ponent to compact readily alone. The non-coal component is mineral matter, usually expressed 45 as ash. Amounts of ash up to 20 per cent do not decrease the efiiciency of briquetting.

Illinois coals contain to per cent clarain, 10 to 20 per cent vitrain, 1 to 10 per cent fusain, and 5 to 15 per cent ash. These naturally occurring proportions are within the operating range.

It is therefore an object of this invention to form strong stable briquettes from coal without, the aid of added binders. 55

while Another object of this invention is to prepare strong stable briquettes from raw bituminous coal without bindersor carbonization of the fuel.

Another object of this invention is to provide a commercially practicable process for producing briquettes of bituminous coal that is operative at an economic cost.

A further object of this invention 'is to provide stable briquettes of bituminous coal which will not disintegrate upon heating by subjecting bituminous coal fines-to impact pressures.

A further object of this invention is to provide a process for producing strong stable bituminous coal briquettes.

Other and further objects of this invention will be apparent to those skilled in the art from the following specification and annexed sheets of drawings which form a partof this specification.

It should be understood that the optimum impact pressures, preheating temperatures and times of preheating will vary with each type of coal to be treated. As a general proposition, however, it may be stated that any bituminous coal heated to a. temperature between degrees and 400 degrees C. over a period between five minutes to'one hour will form a stable briquette with a diameter of from one totwo inches and a thickness from to 1 inches when subjected to an impact pressure such as is produced by a 500 lb. weight dropped by gravity a distance of three to six feet onto a die containing the heated coal. This is equivalent to an impact blow of from 1500 to 3000 foot-pounds to form a briquette averaging about 0.1 lb. in weight or an impact blow of from 15000 to 30000 foot-pounds to form a one pound briquette. Thus an impact blow of from 1500 to 3000 foot-pounds is used for each 0.1 pound of coal impacted since no substantial loss of weight of the coal being impacted occurs during the impaction. Subjecting bituminous coal to temperatures substantially above 400 degrees C. results in a volatilization.

of the volatile matter without destroying .the briquetting properties of the coal. For example, if part of the volatile matter is driven off from the coal by heating to temperatures above 500 degrees C. and the coal is then impacted in dies at temperatures within the range of 100 degrees to 400 degrees C., a smokeless fuel briquette of surprising stability and mechanical strength is formed. Smokeless briquettes produced according to this modification of my invention have heating capacities and burning qualities equal to anthracite coal and. superior to the highest grade bituminous lump coals.

For purposes of comparing the mechanical strength of briquettes produced according to this invention, a standard tumbling barrel containing bafiie plates and flint pebbles was selected for indicating the relative losses in weight caused by abrasion of the briquettes. All tests were run in the same barrel rotated at the same speed of forty revolutions per minute for two minutes. The comparative mechanical strength of the briquettes and lump coal tested is indicated by the per cent loss in weight of the briquettes. This abrasion loss is referred to as tumbling loss in the diagrammatical curves of the accompanying sheet of drawings which indicate the efiect of variations in impact pressure, preheating temperatures, and preheating time on the mechanical strength of the briquettes.

On the drawings:

Figure 1 is a diagrammatic illustration showing the .type of curves obtained by plotting the tumbling loss of the briquettes as ordinates and the impact pressure, expressed as height of drop of a 500 lb. weight; as abscissae.

Figure 2 is a diagrammatic illustration of the type of curves obtained by plotting tumbling loss of the briquettes as ordinates and preheating temperature as abscissae.

Figure 3 is a diagrammatic illustration of the type of curves obtained by plotting tumbling loss as ordinates and preheating time as abscissae.

Figure 4 is a diagrammatic illustration showing the tumbling loss effects by forniing briquettes from coal heated to temperatures of 500 C. and above and impacted at 300 C.

Figure 5 is an elevational view of an impact machine that may be used to form the briquettes of this invention.

Figure 6 is a fragmentary, vertical cross-sectional view, with parts in elevation, of another form of impact machine suitable for forming the briquettes of this invention. I

Figure '7 is a vertical cross-sectional view of a die, suitable for shaping the briquettes of this invention when subject to impact in machines such as shown in Figure 5.

Figure 8 shows views of various shapes of briquettes that may be produced according to this invention. I

As shown on the drawings:

,In Figure 1 the reference numeral l0 indicates the curves obtained by plotting the per cent tumbling loss of briquettes obtained by impact pressures obtained by dropping a 500 lb weight by gravity for distances from two to five feet.

The briquettes formed to provide all data herewithin described are 1.5 inches in diameterand 1.2 inches thick, weighing about 45 grams. The briquettes used in plotting curve I!) were formed tab from Washington county, Illinois, bituminous 40 coal.

The reference numeral l l indicates a corresponding curve obtained from briquettes formed of Franklin county, Illinois, coal which represents a higher grade bituminous coal.

Franklin county coal has a higher 13. t. u.

value and a lower volatile matter content than I ington county coal. .In plotting this curve, the

Washington county coal was preheated for ten minutes at the temperatures indicated in a rotary ovenbefore being subjected to an impact pressure obtained by dropping a. 500 lb. weight for a. distance of four and one-half feet onto a die containing the heated coal. It will be noticed that the lowest tumbling loss occurs when the coal was heated at temperatures between about 225 to 275 C.

The reference numeral l3 in Figure 2 indicates a. corresponding curve for Franklin county Illinois coal. This shows that the tumbling loss is lowest when the coal is heated at temperatures between to 350 C.

In Figure 3, the refer'encenumeral M indicates the curve obtained by plotting the tumbling loss of briquettes formed from Washington county coal that has been preheated to 250 C. for various lengths of time. The heating time has b en plotted as abscissae and the tumbling loss as This curve shows that the tumbling ordinates. loss is lowest when Washington county coal is heated at 250 C. for a period of time between ten and forty minutes.

The reference numeral l5 in Figure 3 indicates the curve obtained by plotting the tumbling loss of briquettes formed from Franklin county,-

Illinois coal which have been heated for various periods of time. This curve shows that the tumbling losses are lowest when the preheating at 250 C. is maintained only for about ten mina two minute treatment therein at forty revolutions per minute. This identical treatment applied to selected lumps of raw coalcut from natural benches shows that the tumbling loss for Franklin county coal varies from .9 to 1.4 per cent while the tumbling loss of Washington county coal was about 2.6. It is evident from a comparison of these results that the briquettes of my invention compare favorably in mechanical strength with natural lumps of coal from which they are obtained.

While the operative conditions will vary considerably depending upon the nature or grade of the coal being treated, it is evident that a pre- 4 ferred range of conditions for bituminous Illinois coal of size or less is a preheat treatment at temperatures between. 150 and 350 C. for a period of time between ten minutes to forty-five minutes, with an impact forming pressure obtained by dropping a 500 lb. weight between four and five feet. Impact pressure greater than those obtained by dropping a 500 lb. weight about five feet result in weaker briquettes. Likewise, variations in temperature and time conditions outside of this preferred range result in weaker briquettes. It should be understood. however, that the process is nevertheless operative outside of this preferred range and the above indicated broader range.

It has been indicated above that the heating of bituminous coal to temperatures above 500 0. results in the elimination of volatile matter. In

, Figure 4, the reference numeral l6 indicates the 4 /2 feet. This curve shows that at temperatures between 500 C. and 550 C., the loss of volatile matter is increased from about 15 to 24 per cent while the tumbling loss is also increased from about 2 to 9 /2 per cent. The elimination of the volatile matter by the preheating at the temperatures indicated results in the production of smokeless fuel briquettes since considerable portions of the volatile or smoke producing matter have been eliminated before the coal is formed into briquette shape. The curve. indicates that about half of the volatile matter of a bituminous 5 heating in a reducing atmosphere in which there is no oxidation or ashing of the coal, or in the state of reduced volatile mattercontent by carbonization in which the volatile matter is eliminated in an oxidizing atmosphere in which some 20 ashing of the coal take place. The briquetted product therefore may be composed of raw coal or of a treated coal composition in which the volatile matter has been reduced to a degreesufiicient' to form a smokeless fuel. The reduction 25 in, volatile matter, as indicated above, may occur under reducing or oxidizing conditions.

While the results shown in the above referred to curves have all been obtained by the use of a single impact, it should be understood that the process may also be practiced by the use of multiple impacts. However, experiments have shown that the subsequent impacts tend to shatter the coal particles which have been bound together by the first impact. A series of high frequency impacts is therefore undesirable in my process although it has been proposed in some prior art. practices.

As shown in Figure 5, the impact blow may be obtained by the use of a falling weight 20 slid- 40 able freely in guide arms 2| onto a briquettedie 22. The weight 20 may be lifted by an electro magnet 23 raised and lowered by a cable 24 operated by a motor 25 on top of the guide arms or standards 2|. It is obvious in this device that 46 when the electro-magnet 23 has been lifted to-' gether with the weight 20 to the top of the guide arms 2| that the magnet may be de-energized to allow the weight 20 to fall on top of the die 22, thereby impacting the heated coal in the die. 50

In' Figure 6, an alternative apparatus for applying the impact pressure is indicated. According to this device, a motor driven piston 30 driven through a rod 3! by a motor (not shown) is slidable in the cylinder 32 of a forming die 33. The 5 piston 30 impacts the heated coal in the cylinder 32 to form the briquettes of this invention.

In Figure '7, the reference numeral 40 indicates generally a form ofimpaction die that has been successfully used in forming briquettes in 60 the apparatus shown in Figure 5. The die 40 corresponds with the die 22 shown in Figure 5,

and comprises an impact cylinder -4| against which the falling weight may contact, a top impact ram 42 slidable in a cylinder 43 defined by 65 an inner sleeve 44. The cylinder 43 provides the space 05 for the briquette. A bottom plunger 46 extends from beyond an outer sleeve 41' as shown. The sleeve 41 is reinforced at the top and bottom by a flange 48. 70 A heating coil 49 may be wound around the sleeve 41 for maintaining the die at the proper temperature. A well 50 is provided through the sleeve 41 for receiving a thermocouple or other temperature indicating device. 75

When the impact from the falling weight is received on the cylinder 41 it is transferred to the bottom plunger 46 and the coal within the space 45 is immediately compacted into briquette form. It is evident from the above description that I have provided a process for producing novel briquettes composed of raw or treated fuel. The

briquettes of this invention are formed. without the aid of added binders and have great strength and stability. The briquettes may be readily manufactured oh a commercial scale with great economy because a single impact or instantaneous pressureis sufiicient to form the briquettes whereas in prior art practices pressure has always been applied to the coal for considerable periods of time. The coal may be preheated to temperatures between and 400 C. without removing substantial amounts of, volatile matter.

Smokeless fuel briquettes may be formed by heating the coal at temperatures sufiicient to eliminate part of the volatile matter and then forming the briquette fromthe coal after it has cooled to temperatures within the range 100 to 400 C'.

As shown in Figure 8, the briquettes may be formed in any one of many suitable shapes, for

example, a cylinder I, a cube 2, a sphere 3, or a spheroid 4.

The apparatus described for forming the bri-' quettes merely indicates means for forming a fuel briquette by a single impact. It is obvious, however, that the apparatus may be added to so that a single impact will produce the formation of many briquettes.

Having now described my invention, I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the prior art.

I claim as my invention:

1. The process of forming bituminous coal briquettes, which comprises heating bituminous coal' 2. The process of forming strong, stable bitu minous coal briquettes, which comprises heating bituminous coal of size or less to temperaturesbetween to 350 'C. for about ten minutes to forty-five minutes and subjecting the soheated coal to a single impact equivalent to that obtained by dropping onto a mass of coal suflicient to form a briquette from 1 to 2 inches in diameter and from to 1 inches in thickness'a 500 lb. weight dropping by gravity for a distance between 4 to 5 feet.

3. The process of preparing smokeless fuel briquettes from bituminous coal, which comprises heating the coal to liberate part-or the volatile matter therefrom, cooling the heated coal to temperatures between 100 and 400 C., and subjecting the coal at these temperatures to a. single 6 impact equivalent to that obtained by dropping onto a mass of coal suflicient to form a briquette from 1 to 2 inches in diameter and from V; to 1% inches in thickness a 500 lb. weight by gravity for a distance between 3 to 6 feet. 10

4. The process of forming strong, stable briquettes from bituminous coal containing considerable amounts of volatile matter, which comprises heating said coals to remove a portion of the volatilematter, cooling the so-heated coal to temperatures between 150 to 350 C., and impacting the coal at said temperatures in a die by a single impact equivalent to a 500 lb. weight falling by gravity a distance between 3 to 6 feet onto a mass of coal sufiicient to form a briquette 20 from 1 to 2 inches in diameter and from A to 1 inches in thickness.

' 5. The process of forming carbonized smokeless fuel briquettes, which comprises heating bituminous coal to temperatures between 500 and 5 550 C. for about ten minutes, cooling the heated coal to temperatures between 150 and 350 C.

' and subjecting-the cooled coal to a single impact jecting the so heated coal to a single impact blow equivalent to about 1500 to 3000 foot-pounds for 40 each 0.1 pound -of coal compacted and thereby forming a dense briquette.

'7. The process of forming strong, stable briquettes without the aid of added binders from bituminous coal containing considerable amounts 45 of volatile matter, which comprises heating said coals to remove a portion of the volatile matter, cooling the so heated coals to temperatures be tween 150 arid 350 C., and subjecting the coals at said temperatures in a die to a single impact 50 blow of about 1500 to 3000 foot-pounds for each 0.1 pound of coal compacted and thereby forming a dense briquette.

8. The process of forming briquettes from low grade bituminous coal, which comprises heating 55 said coal to temperatures over 500 C. for about ten minutes under reducing conditions to remove part of the volatile matter therefrom, cooling the so-heated coal below its plastic state and impacting the cooled coal in a confined space to a tem- 60 porary plastic state by a "single impact blow equivalent to about 1500 to 3000 foot pounds for each 0.1 pound of coal impacted and thereby forming a dense briquette.

ROBERT J-. PIERSOL. 65 

